Carl & Jerry: Lie Detector Tells All
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In this episode of John T. Frye's Carl & Jerry technodrama series, titled "Lie Detector Tells All," Carl Bishop has designed a crude lie detector using a vacuum tube voltmeter (VTVM) to measure the change in resistance of the human body when situations of stress and/or duress cause perspiration, which affects the resistance to current flow. A VTVM was required because its high input impedance (a few megohms) was necessary to accurately measure body resistance. In contrast, a standard electromechanical meter movement (aka D'Arsonval) only provides a few ohm of resistance. When this appeared in a 1955 issue of Popular Science magazine, a VTVM was much more expensive than the D'Arsonval-based meter. Even a low-end modern multimeter uses a field effect transistor (FET) - of the junction (JFET) or metal oxide (MOSFET) type - with an input impedance in the tens to hundreds of ohms. The story takes a comical turn when Jerry's parents volunteer (reluctantly) to be test subjects for the invention. Interestingly, the Wikipedia entry for the polygraph refers to it as "junk science," while noting that many countries' law enforcement agencies use it to some degree. Carl & Jerry: Lie Detector Tells All
Jerry, stretched out on the worn old - leather- covered couch in his basement laboratory, was jerked out of his pleasant reverie by the banging of the cellar door against the wall as his chum and neighbor, Carl Anderson, came striding in. "Hey, Jer, how do you give artificial respiration to a night crawler?" Carl asked excitedly as he dangled a very limp worm, a full ten inches long, directly in front of Jerry's crossing eyes.
Carl dangled a very limp worm directly in front of Jerry's crossing eyes... "Get that young snake out of my face," Jerry commanded as he struggled to a sitting position; "and what kind of a stupid question is that?" "It's not stupid," Carl denied heatedly. "If we can just bring Old Droopy here and his buddies back to life, we're on our way to being millionaires!" "Again?" Jerry said languidly as he smothered a yawn. "Let's hear your latest lid-flipper." "On their drive last Sunday, my folks gathered up a couple of bushels of walnuts along the road," Carl explained. "I have to hull them by driving them through a knothole in a board. As you know, this is a messy business; so to avoid getting any more of the sticky, staining walnut hull juice on me than necessary, I decided to run water over the crate of nuts before starting. The water filtered down through them and spread over the ground. In nothing flat, worms started wriggling up out of the wet earth. Apparently that walnut hull juice gave them a real hotfoot, for they were in such a hurry to get away from it that they popped to the surface and practically stood on their tails. "I grabbed them faster than a woman snatching up the contents of her spilled purse, but in just a few minutes they stopped wriggling. I washed them off in clear water and even tried brushing Droopy here with some of Mom's super-gentle soap powder, but he refuses to come around. I figure artificial respiration is the last hope; if you will just point out where his ribs are so I'll know where to put my thumbs, we'll get started. If we can revive him, we're in business. We can grind up the walnut hulls and sell a small vial of the powder for a dollar. The purchaser need only mix a few gallons of water with this powder and pour the solution on the ground. After a few minutes, he can pick up a couple of cans of fish worms and be on his way. Think of it: no strain, no pain, and no spading!" "Well," Jerry commented, as he gingerly prodded with his forefinger the worm Carl had placed on the couch beside him, "all I can suggest is that you include a bottle of embalming fluid with every vial of that walnut hull powder. That's the only thing that will 'save' Droopy now. How come you're all at once money mad, anyway?" "I've decided we need an oscilloscope for our laboratory," Carl announced importantly. "After boning up on this instrument, I'm convinced there are any number of interesting experiments and important tests that can be made with it. What's more, it would come in mighty handy for checking my transmitter, especially now that I'm starting to build a single-sideband suppressed-carrier job. We can buy a scope kit that will fill our needs nicely for around fifty dollars, but first we've got to latch on to the fifty." "I commend your ambition, but I decry your methods," Jerry announced pompously. "You must learn to think electronically. If we need new electronic equipment, let's make the electronic equipment and know-how we already have pay for it." "Such as how?" Carl demanded. "It's all arranged," Jerry said, with elaborate casualness. "The Acme TV Service Shop is opening this weekend and holding open house on both Friday and Saturday. I talked the guy who owns it into a big deal of letting me set up a lie detector there in the store and give free lie-detector tests to anyone who wants to try it. He figures this will be just the unusual type of gimmick to draw a crowd; he'll pay me 25 bucks for giving tests Friday night and all day Saturday." "Oh fine! Now all you gotta do is buy a lie detector!" "No such thing. Back in May, 1955, Popular Electronics published an article on how to make a gadget to use with your v.t.v.m. to serve as a lie detector. This is a simple little gadget, and all the parts for it, except the tube and B battery, came out of our junk box. I 'borrowed' these other two items from Dad's portable radio that he won't be using - I hope - until next spring. Come on over to the bench, and I'll show you how it works. Just then, however, Mr. and Mrs. Bishop, Jerry's parents, came in through the inside door leading to the basement storage room. Mrs. Bishop had a bushel basket, and Mr. Bishop carried a spading fork and had the unhappy look of a man reluctantly being prodded into digging up flower bulbs for winter storage. "Well, well, what are our young inventors up to now?" he questioned, with the hysterical joviality of a man snatching at straws to put off the start of an unpleasant job. "I was just going to show Carl how my new lie detector works," Jerry explained. "Show me!" Mr. Bishop insisted. "I always did want to see if those things really could tell when an iron-nerved man like myself chose to toy with the truth." "Well, all right," Jerry agreed. "Just slip these two metal thimbles with the wires attached over the middle fingers on each hand. They are the connecting electrodes that enable the instrument to measure any change in the resistance path between them. When you are emotionally disturbed, as you will be if you try to avoid the truth, the change in your body resistance will be indicated by the swing of this meter pointer on the vacuum-tube voltmeter." With an amused smile, Mr. Bishop slipped the electrodes on his finger tips and watched his son balance the bridge circuit so that the meter pointer rested in the left -hand portion of the scale. "What is your name?" Jerry asked. "Milton Bishop." "Where do you live?" "1810 Spear Street." "What do you work at?" "I'm an architect." Mrs. Bishop, who had been impatiently watching the quiet needle of the v.t.v.m., broke in with: "Let my try. You told me you couldn't come home for dinner last night because you had to work late at the office. Is that true?" "Certainly," was Mr. Bishop's prompt reply as he turned to smile fondly at his wife. For a split second nothing happened, and then the meter started to climb. As it reached full-scale, Mr. Bishop turned harriedly from the accusing meter to the still more accusing eyes of his wife. "I did work late, a whole half hour," he insisted; "then a bunch of us fellows went over to Vic Cline's to see his new twenty-five horsepower outboard motor. A little game started somehow ... and the time sort of got away from us . As his voice trailed off in this weak explanation, he jerked off the thimbles as though they were red-hot and flung then down on the bench. "Well, come on, Iron Nerves; let's make with the spading fork," Mrs. Bishop suggested with a mocking, victorious smile.
For a split second nothing happened, then the meter started to climb... "Oh, no, you don't!" her husband exclaimed. "Let's see you try the lie detector, Mabel." In spite of her protests, Mr. Bishop slipped the thimbles on her fingers and watched impatiently while Jerry rebalanced the bridge circuit. "Your name, Madam?" Mr. Bishop snapped. "Mabel Bishop." "Your age?" "Thirty-seven -- no, I mean thirty-eight," Mrs. Bishop hurriedly amended, as the meter pointer began a threatening upward movement. "Just a few minutes ago I noticed a long scratch on the right rear fender of the car. Would you know anything about that?" "I was intending to mention that to you," Mrs. Bishop began calmly. "It must have happened in the supermarket parking lot. I didn't notice it until I came home... or at least I don't remember noticing it, or if I did I forgot about it... or maybe I do remember hearing a little noise as I was backing out of the garage... She kept talking more and more frantically in her effort to stop the relentless march of the meter pointer up- scale, but it was no use. In spite of Jerry's repeated rebalancing of the bridge, the pointer kept crawling up. "I thought so!" Mr. Bishop gloated. "For your information, that scratch is just level with the hasp on the door frame." "Maybe we had better go and dig those bulbs now," Mrs. Bishop remarked quietly, as she removed the thimbles and placed them gently on the bench. Obediently, but with a smirk still on his face, Mr. Bishop followed her outside. "Boy, that thing really works!" Carl said enthusiastically, as Jerry's parents closed the door behind them. "Yes," Jerry agreed, as he slipped on the thimbles and rebalanced the instrument; "it is an interesting little device. Of course a polygraph; as a laboratory-type lie detector is called, is quite a bit more complicated than this. It records the reaction of the person being examined to each question by means of scribing pens tracing on moving sheets of paper; and sometimes the pulse rate, respiration, and other factors are recorded as well as the skin resistance; but for our purposes -" He turned around as he heard the outside door quietly open to admit his father. "I'm supposed to be after another basket," Mr. Bishop announced in a hushed conspiratorial voice; "but I wanted to have a word with you two about that lie detector you've built up. A man isn't safe with a vacuum tube snitcher like that lying around. We men know that a little white lie is necessary now and then; so that thing has gotta go. What will you take to dismantle the gadget? Ten dollars?" "Well, I don't know," Jerry said hesitantly. "After all, there is a considerable investment in parts -" Quickly, but unobtrusively, he wriggled his fingers out of the thimbles as the tell -tale meter pointer started upward. "Okay, I'll make it fifteen dollars," Mr. Bishop said hurriedly, as he took out his wallet; "but remember this is just between us men. Not a word to your mother." He got another basket, shot a baleful glance at the lie detector resting on the bench, and went outside again. He had barely closed the door behind him when Mrs. Bishop opened the other door. "I was just looking for your father," she remarked casually, as she sat down on the couch from which Carl thoughtfully snatched the carcass of Old Droopy before she noticed it. "I believe I'll rest a bit, though, if you boys don't mind." "Sure, Mom; glad to have you," Jerry said. "You know," she commenced, in a very offhand manner, "I've been thinking about that amusing little toy you have built up; and I'm not at all sure you boys should be playing with such a thing. While we know it is just a plaything, an electronic tattletale like that could cause trouble. In fact, I'm afraid that it has already embarrassed your poor father; and we can't have that, now, can we? If you'll tear it up, I think I might be able to give you, say, ten dollars, to buy something really worth while for your laboratory." "Gee, Mom, that's swell of you; and we'll certainly tear up the silly thing the first of next week," Jerry promised. She reached into her apron pocket and handed over a ten dollar bill, then went out in search of Mr. Bishop. "Why didn't you hold out for fifteen dollars, the way you did with your Dad?" Carl demanded. "You don't haggle with ladies," Jerry explained chivalrously; "and anyway the twenty-five they gave us plus the twenty-five we'll get from Acme TV Service will just buy that new scope kit. There's no use in being a hog about things." "Guess you're right," Carl agreed, "and I've got to take off my hat to you. When it comes to harvesting the old government lettuce, electronics has fish worms beat all to heck!"
Posted March 28, 2024
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By John T Frye, W9EGV
Carl & Jerry, by John T. Frye